We are studying endocrine and metabolic changes which occur as an individual develops from a fetus to a mature adult. We have currently focused on two areas: 1) monthly gonadotropin cycles in premenarchial girls and pubescent boys utilizing radioimmunoassay methods for measuring urinary luteinizing hormone and urinary follicle stimulating hormone and analyzing the data with autoregressive computer techniques, and 2) mineral metabolism in the monkey fetus and human newborn. Calcium kinetics are studied using stable calcium isotopes in the patient analyzed in the laboratory by mass spectrometry. Physiological effects of calcium are studied by measurements of ionized calcium in the blood and in cerebrospinal fluid. Trace element (zinc and copper) analyses are performed by atomic absorption spectrophotometry as part of our studies of nutritional aspects of mineral metabolism in the newborn.